Attachment mechanisms for stabilzation of subsea vehicles

ABSTRACT

Systems and methods for securing a remotely operated vehicle (ROV) to a subsea structure during cleaning, maintenance, or inspection of the structure surface are provided. In one or more embodiments, an attachment mechanism includes a pair of grasping hooks that are raised and lowered when driven by a motorized drive. In one or more embodiments, an attachment mechanism includes a rigid holder having a mechanical stop and connected to a swing arm, the swing arm configured to rotate inward, but not outward beyond the mechanical stop. In one or more embodiments, an attachment mechanism includes a plurality of linked segments in series, each connected at a plurality of pivot points. A pair of wires passes through the plurality of linked segments and connects to a pair of pulleys that extend or retract the wires, thereby rotating the plurality of linked segments.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims the benefit of priority of U.S. Ser. No.62/397,175, filed Sep. 20, 2016, entitled Underwater VehicleConstruction Operation, Coordination, and Control Attachments Thereforand Methods Relating to Same, which is hereby incorporated by referenceas if set forth in its entirety herein.

FIELD OF THE INVENTION

This patent application relates to remotely operated vehicle inspectiondevices, and, more particularly, to mechanisms for securing remotelyoperated vehicles to subsea surfaces.

BACKGROUND

One common way to perform surface inspections of subsea structures suchas pipelines, pilings, risers, and boat hulls is to navigate a remotelyoperated vehicle (ROV), such as by utilizing thruster jets, to theinspection surface, and to then deploy one or more robotic arms havinginspecting tools therein. ROV-based inspections are particularlysuitable for subsea pipelines that are vertically or horizontallyinstalled in the ground, or suspended from a support structure.

It can be a challenge to maintain ROV stability during inspection,especially if the inspection surface is a structure suspended in waterbecause such structures are less stable than seabed-implantedstructures. Specifically, the challenge arises from reaction forcesgenerated upon contact of inspection tools to the surface beinginspected or cleaned. Since the ROV floats underwater, the ROV isparticularly sensitive to such reaction forces due to buoyancy effectsand the reaction forces can easily push the ROV backward to destabilizeit. In particular, deploying cleaning jets, rotating brushes, and othermarine life cleaning tools at an inspection surface imparts strongreaction forces to the ROV robotic arm, which leads to frequentdestabilizations. Re-stabilizing the ROV or counteracting the reactionforce can be accomplished by activating thrusters to provide acontinuous thrust force in opposition to the reaction force. However,increased thruster use has several drawbacks. For instance, activatingthe thrusters depletes ROV battery power, thereby reducing ROV uptime.Constant re-stabilizing also agitates the seabed and churns the water,which reduces operator visibility, and introduces costly delays fromcontinually having to reorient the robotic arm to the inspectionsurface.

As such, there exists a need for mechanical solutions to improvestabilization of ROVs during inspection and cleaning tasks withoututilizing thrusters, in particular when such tasks are performed onpipelines. It is in regard to these issues that the present applicationis provided.

SUMMARY OF THE INVENTION

According to a broad aspect of the invention, attachment mechanisms forclamping a remotely operated vehicle to a subsea structure surface areprovided.

In one aspect of the invention, embodiments of the attachment mechanismare suitable for securing a remotely operated vehicle (ROV) to a subseastructure. The attachment mechanism includes a motor for generating arotational force. Further, the attachment mechanism includes a worm geardrive system driven by the motor, the worm gear system including adriveshaft, a worm screw, a wormshaft, a worm wheel, and a first pair ofbevel gears. The driveshaft includes a first end and a second end, thefirst end coupled to the motor, and the worm screw is adjacent to thesecond end, the worm screw having a plurality of teeth disposed alongits outer circumference and driven by the generated rotational force torotate. The wormshaft includes the worm wheel disposed at a centralportion of the wormshaft, the worm wheel being circumferentiallythroated to mesh with the plurality of teeth of the worm screw, suchthat when the worm screw is driven by the generated rotational force,the wormshaft rotates correspondingly. The first pair of bevel gears iscoaxially disposed at each end of the wormshaft and the first pair ofbevel gears bears a plurality of external teeth at their pitch surfaces.

Continuing with this aspect of the invention, embodiments of theattachment mechanism include a pair of grasping hooks, horizontally andvertically canted at an angle relative to operating orientation of theROV in a mirrored orientation to one another, each grasping hook havinga first end and a second end that is free. Additionally, the attachmentmechanism includes a pair of hookshafts, a first end of each hookshaftbeing coupled to the first end of each grasping hook, the pair ofhookshafts being oriented at an angle relative to the wormshaft.Moreover, a second pair of bevel gears is coaxial with and surroundingthe pair of hookshafts and disposed adjacent to a second end of eachhookshaft, the second pair of bevel gears bearing a plurality ofexternal teeth at their pitch surfaces. In one or more embodiments, theattachment mechanism is arranged such that the external teeth of thefirst pair of bevel gears and the external teeth of the second pair ofbevel gears mesh at a meshing angle, such that when the motor drives theworm gear system, the rotational force is transferred to the hookshaftsto raise or lower the grasping hooks and to clamp the second end of thegrasping hooks about the subsea structure.

In another aspect of the invention, embodiments of an attachmentmechanism suitable for securing a remotely operated vehicle (ROV) to asubsea structure are provided. In one or more embodiments, theattachment mechanism includes a rigid holder having at first end mountedto the ROV and a second end that is free, the rigid holder having amechanical stop disposed at the second end and a pivot point adjacent tothe second end. Additionally, a swing arm is coupled to the rigid holderat the pivot point, the swing arm having a rolling element embeddedtherein and having a rest orientation. Further, a spring means isdisposed between the mechanical stop and the swing arm, therebyproviding a tension force to the swing arm. In one or more embodiments,the attachment mechanism is arranged such that upon contact to thesubsea structure, a reaction force causes the swing arm to rotate inwardtoward the ROV until the tension force overcomes the reaction force,causing the swing arm to rotate to the rest orientation.

In another aspect of the invention, embodiments of an attachmentmechanism suitable for securing a remotely operated vehicle (ROV) to asubsea structure are provided. In one or more embodiments, theattachment mechanism includes a plurality of linked segments connectedin series by a plurality of pin joints disposed between each linkedsegment, the plurality of linked segments each having a mechanical stopconfigured to prevent the plurality of linked segments from rotatingthrough a certain angle. Moreover, a flexible extension wire isconnected to an extension pulley at one end and supported through theplurality of linked segments above the plurality of pin joints. Further,a flexible contraction wire is connected to a retraction pulley at oneend and supported through the plurality of linked segments below theplurality of pin joints. The attachment mechanism additionally includesa first locking mechanism disposed at the extension wire and a secondlocking mechanism disposed at the retraction wire, the first and secondlocking mechanisms being configured to lock the plurality of linkedsegments in place by locking the extension wire and the contraction wirein place. In one or more embodiments, the attachment mechanism isarranged such that the extension pulley and the retraction pulley rotateto extend or retract the extension wire or retraction wire to actuatethe plurality of linked segments.

In another aspect of the invention, a method of attaching a remotelyoperated vehicle to a subsea surface is provided. In one or moreembodiments, the method implements a remotely operated vehicle initiallyin a rest orientation. The ROV is of a type having a rigid holdercoupled to a swing arm with a rolling element embedded therein and aspring means disposed between the rigid holder and the swing arm. Themethod includes contacting a first portion of the surface of a subseastructure with a first face of the rolling element. The method advancesthe remotely operated vehicle in the direction of the subsea structuresuch that the first face of the rolling element contacts a secondportion of the subsea structure and causes the swing arm to pivot towardthe rigid holder and increase a tension force in the spring means. Theremotely operated vehicle is then advanced in the direction of thesubsea structure such that the first face of the rolling element passesan apex of the subsea structure and the tension force stored in thespring means is greater than a normal force exerted on the swing arm bythe subsea structure. Further, the swing arm pivots away from the rigidholder back toward the rest orientation upon release of the tensionforce in the spring means. In some embodiments, the pivoting of theswing arm away from the rigid holder back toward the rest orientationcauses the swing arm to contact a third portion of the subsea structurethat is approximately diametrically opposed to the first portion of thesubsea structure.

These and other aspects, features, and advantages of the invention canbe further appreciated from certain embodiments of the inventiondescribed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawing figures illustrate exemplary embodiments andare not intended to be limiting of the invention. Among the drawingfigures, like references are intended to refer to like or correspondingparts.

FIG. 1A illustrates a isometric side view of an attachment mechanism forsecuring a ROV to a horizontally oriented subsea structure in accordancewith at least one embodiment of the present application;

FIG. 1B illustrates an isometric side view of the attachment mechanismof FIG. 1A as secured to a vertically oriented subsea structure;

FIG. 2 illustrates a schematic view of an actuation system for anattachment mechanism in accordance with at least one embodiment of thepresent application;

FIG. 3 illustrates a side view of an attachment mechanism for securing aROV to a subsea structure in accordance with an alternative embodimentof the present application;

FIG. 4A illustrates a side view of the attachment mechanism of FIG. 3during a securing operation to a subsea structure;

FIG. 4B illustrates a side view of the attachment mechanism of FIG. 3during a continuation of the securing operation of FIG. 4A to a subseastructure;

FIG. 5A illustrates a side view of an attachment mechanism for securinga ROV to a subsea structure in accordance with an alternative embodimentof the present application;

FIG. 5B illustrates a side view of an attachment mechanism of FIG. 5Bduring a securing operation to a subsea structure; and

FIG. 5C illustrates a side view of two exemplary linking segments of theattachment mechanism of FIGS. 5A and 5B.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION

In accordance with one or more aspects of the invention, embodiments areprovided that are directed to attachment mechanisms to a robotic arm ofa remotely operated vehicle (ROV) that improve ROV stability duringsubsea structure inspection and cleaning. In particular, the inventionis described in connection with one or more embodiments in which the ROVis secured or clamped to the subsea structure to be inspected (e.g., apipeline) by an attachment mechanism in such a way as to passivelycounteract destabilization of the ROV by reaction forces generatedduring inspection and cleaning activity. The provided attachmentmechanisms use little to no power by latching to the subsea structure,thereby maintaining ROV stability with limited thruster utilization and,thus, preservation of battery life. Further, in one or more embodiments,the attachment mechanisms provided herein have a structure that issmaller in size than conventional clamping or other mechanisms such thatthe attachment mechanisms can be advantageously implemented by small,lightweight class ROVs, such as electric ROVs, general class ROVs,inspection class ROVs, observation class ROVs, and other batteryoperated ROVs of the type that do not use an umbilical cord to drawpower from an above surface power source.

In one or more embodiments, the attachment mechanism is a motorizedgrasping type device in which one or more ambulatory grasping hooksextend from the front inspection-facing portion of the ROV. In one ormore embodiments, the grasping hooks are configured to have a curvedshape that engages a round or cylindrical subsea structure, such as apipeline. The hooks are actuated from an open position to a closedposition by an actuation system. In the open position, the ROV is notsecured to the structure, whereas in the closed position the ROV issecured to the structure. In one or more embodiments, the actuationsystem comprises a motor, one or more bevel gears, and a worm gear drivesystem arranged to raise or lower the grasping hooks.

In one or more embodiments, the attachment mechanism comprises a rigidholder coupled to a rotatable swing arm designed to contact the subseastructure and adapt to the subsea structure surface until secured inplace by a mechanical stop. The swing arm comprises a rolling element,such as one or more rollers. The swing arm is coupled to the rigid armat a pivot point and by a spring means disposed between the swing armand the mechanical stop. The mechanical stop restricts the rotation ofthe surface arm in one direction.

In one or more embodiments, the attachment mechanism comprises aplurality of linked segments, connected in series to one another by apin joint. The pin joint and the shape of the linked segments functionas a mechanical stop, such that plurality of linked segments can rotateinwards in a finger-like movement, but cannot extend much beyond astraight, horizontal extension.

The invention is now described with reference to the accompanyingdrawings, which form a part hereof, and which show, by way ofillustration, example implementations and/or embodiments of the presentinvention. It is to be understood that other embodiments can beimplemented and structural changes can be made without departing fromthe spirit of the present invention. Among other things, for example,the disclosed subject matter can be embodied as methods, devices,components, or systems.

Furthermore, it is recognized that terms may have nuanced meanings thatare suggested or implied in context beyond an explicitly stated meaning.Likewise, the phrase “in one embodiment” as used herein does notnecessarily refer to the same embodiment and the phrase “in anotherembodiment” as used herein does not necessarily refer to a differentembodiment. It is intended, for example, that claimed subject matter canbe based upon combinations of individual example embodiments, orcombinations of parts of individual example embodiments.

With reference now to FIGS. 1A and 1B, an attachment mechanism 100 forsecuring a ROV to a subsea structure in accordance with at least oneembodiment of the present application is provided. In one or moreembodiments, the attachment mechanism 100 is coupled to a ROV 105 so asto comprise an accessory for the ROV. Coupling to the ROV can be in anyconventional way, such as by bolts. Advantageously, the attachmentmechanism 100 can be attached to small, lightweight ROVs such aselectric ROVs, general class ROVs, inspection class ROVs, observationclass ROVs, and other battery operated ROVs. In the exemplaryembodiment, the attachment mechanism 100 is designed to surround andclamp the ROV to a cylindrical pipeline (e.g., horizontal pipeline 107,as shown in FIG. 1A; vertical pipeline 109, as shown in FIG. 1B), thoughthe attachment mechanism can be configured to clamp to other subseasurfaces such as pilings, or hulls, and can be suitably configured forclamping to target objects of arbitrary shape.

In one or more embodiments, the attachment mechanism 100 includes a pairof grasping hooks 110 a, 110 b (or “curved members”). The grasping hooks110 include a first or upper end 115 and a second, or lower free end120. In one or more embodiments, the grasping hooks 110 extend from eachof their first ends 115 to their second ends 120 along a circular arc ofat least 180° so as to cooperate with the abutment point of theattachment mechanism 100 to the ROV 105 in such a way as to generallysurround and clamp to the pipe 107, at least along one side of the pipeas illustrated in FIG. 1A. In the exemplary embodiment illustrated byFIGS. 1A and 1B, the pair of grasping hooks 110 a, 110 b are canted bothin horizontal and vertical planes relative to the operating orientationof the ROV. Advantageously, forming the grasping hooks with a cant ortilt allows the attachment mechanism 100 to secure the ROV 105 to bothhorizontally and vertically oriented subsea structures without needingto reorient the ROV or any attachment arms. This is because the tilt ofthe grasping hooks 110 allows different portions of the hooks to attachto a subsea structure. For example, as shown in FIG. 1A, the undersideof each grasping hook 110 encircles the curvature of a horizontallyoriented pipe 107. Then, as illustrated by FIG. 1B, the ROV 105 canattach to a vertically oriented pipe 109 by encircling the pipe with theinside edges of the grasping hooks 110. Attaching to either ahorizontally oriented pipe 107 or a vertically oriented pipe 109 isthereby accomplished without changing the orientation of the ROV.Advantageously, this reduces ROV 105 thruster use, which is desirablefor smaller, lightweight ROVs. Additionally, approaching at an angleensures that the grasping hooks 110 wrap around a subsea structure in atighter fashion than if the hooks were to be mounted orthogonal to thepipe.

In one or more embodiments, the tilted orientations of the first hook110 a and the second hook 110 b are such that the orientation of thepair of grasping hooks is mirrored. For example, if the first hook 110 ais tilted 45 degrees from both the horizontal and the vertical planes,the second hook 110 b is tilted negative 45 degrees from both thehorizontal and the vertical planes. In a particular embodiment, thegrasping hooks 110 are formed with a cant or tilt of 45 degrees. Thisangle provides the most versatility for the ROV to grasp onto bothhorizontal and vertical pipes (e.g., pipelines 107, 109), though inpractice, the cant or tilt of the grasping hooks 110 can vary a smallamount (e.g., +/−5 degrees) from 45 degrees and is still effective insecuring the ROV 105 to both horizontal and vertical orientedcylindrical surfaces.

With reference now to FIGS. 1A, 1B and 2, the grasping hooks 110 aremechanically coupled to a worm gear drive system 200 housed with ROV105. The worm gear drive system 200 is a motorized arrangement of gearsand shaft components that when driven, serves to actuate the graspinghooks 110 to pivot upwardly and downwardly in a vertical plane in an arcto facilitate engagement with the subsea surface e.g., horizontalpipeline 107, vertical pipeline 109) and secure the ROV 105 in placeduring inspection of the subsea surface. In one or more embodiments, theworm gear drive system 200 includes a motor 205 that drives an enmeshedworm screw 210 and worm wheel 215 combination (a “worm gear”) to rotatean elongated wormshaft 220 having a first pair of bevel gears 225 a, 225b (and more generally bevel gears 225) disposed at each end. In thisway, torque amplification is provided to the wormshaft 220. The wormwheel 215, in one or more embodiments, is disposed about thecircumference of and coaxially with the wormshaft 220. In one or moreembodiments, the worm wheel 215 is located at the center of thewormshaft 220. One or more bearings can be included about thecircumference of the wormshaft 220. For example, a bearing can bepositioned adjacent to each of the bevel gears 225 a, 225 b. The bevelgears 225 are designed to have a pitch angle of less than 90 degrees andto engage with a similarly pitch angled second pair of bevel gears 235a, 235 b (and more generally bevel gears 235) that are disposed at anend of a hook shaft 230, The hook shaft 230 is coupled to the graspinghooks 110 and thus, when driven by the motor, this sequence ofmechanical engagements serves to raise or lower the grasping hooks 110.

It can be appreciated that while the illustrated embodiments anddiscussion herein refer to “pairs” of hooks, hookshafts, and bevelgears, the advantages of having more than one hook and correspondinghookshaft and bevel gear extend more generally to a “set” of hooks,hookshafts and bevel gears. As such, each of the embodiments describedherein can more generally be constructed so as to have a set of hookseach with a respective hookshaft and engaged to a bevel gear, whereinthe set comprises from one to many hooks and hookshafts and possiblymany bevel gears.

More particularly, as shown in the exemplary embodiment in FIG. 2, theworm gear drive system 200 includes a motor 205 that drives a driveshaft207 that is coupled to the motor at a first end. One or more bearingscan be implemented adjacent to the first end of the driveshaft 207 tofacilitate coupling the driveshaft to the motor 205. The dtiveshaft 207is a cylindrical shaft having a portion fashioned into a worm screw 210adjacent to the second end of the driveshaft 207. As the motor 205drives the driveshaft 207, the driveshaft rotates either clockwise orcounter-clockwise about its longitudinal axis. The worm screw 210 thentransfers this rotational motion to a worm wheel 215 that is meshed withthe worm screw.

As shown by FIG. 2, the worm wheel 215 is positioned perpendicular toand meshed with the worm screw 210 to encompass a worm gear, such thatthe rotational motion generated by the motor 205 to the worm screw andtransferred to the worm wheel causes the worm wheel to rotate clockwiseor counter-clockwise about the horizontal longitudinal axis of thewormshaft 220. This in turn causes the wormshaft 220 to rotate about itshorizontal longitudinal axis. To facilitate meshing of the worm gear,the worm screw and the worm wheel can include a plurality of teeth andgrooves machined along their outer circumferences that are sized andshaped to correspondingly couple the worm screw and the worm wheel. Theworm gear can be non-throated (i.e., no grooves machined around thecircumference of the worm screw 210 or worm wheel 215), single-throated(i.e., grooves are machined around the circumference the worm wheel215), or double-throated (i.e., grooves are machined around both thecircumference of the worm screw 210 and the worm wheel 215). In one ormore embodiments, the worm wheel 215 is throated to include a pluralityof teeth disposed along its outer circumference that are sized andshaped to engage with a throated worm screw 210.

A first pair of bevel gears 225 a, 225 b bearing a plurality of externalteeth at their pitch surfaces are disposed coaxially with, and at, eachend of the wormshaft 220. In one or more embodiments, the bevel gears225 are mounted to provide a particular pitch angle. For example, in oneembodiment, the bevel gears 225 have a pitch angle of 22.5 degrees,though other pitch angles can be contemplated depending on the desiredrange of motion for the attachment mechanism 100.

In one or more embodiments, the worm gear drive system 200 generates arotational force that serves to pivot the grasping hooks 110 of theattachment mechanism 100 in an upward or downward motion, therebysecuring the ROV 105 to a subsea surface, Advantageously, the torqueamplification effects provided by worm gear drive system 200 serve as alocking mechanism against inadvertent grasping hook 110 motions. Moresimply, due to the meshing nature of the first bevel gears 225 and thesecond bevel gears 235, without the torque amplification provided by themotor 205, the grasping hooks 110 are held in place. The bevel gears areselected such that during typical use, external forces, such as thosegenerated by the ROV or the grasping hooks 110 during contact with asurface, do not exceed the torque amplification threshold necessary torotate the bevel gears.

To effect grasping hook 110 actuation by the worm gear drive system 200,in one or more embodiments, the first end 115 of the grasping hooks 110defines an aperture or cavity 125 for receiving a first end of a pair ofhook shafts 230 a, 230 b that couple the first end 115 to the ROV 105.In one or more embodiments, the grasping hooks 110 are coupled to theworm gear drive system 200 at the first end 115 via a pin, screw, epoxy,adhesive or other fastener. Each of a second pair of bevel gears 235,bearing a plurality of external teeth at their pitch surfaces, surroundeach of the hook shafts 230 a, 230 b and are disposed at or adjacent to,and coaxial with, a second end of each hook shaft 230. The first pair ofbevel gears 225 and the second pair of bevel gears 235 arecorrespondingly throated (i.e., having grooves sized and shaped to meshwith the plurality of teeth disposed about the circumference of othergears) such that as the first pair of bevel gears rotate, the meshedsecond pair of bevel gears receive the rotational force and rotate inthe opposite direction due to the meshing. This meshing compels the hookshafts 230 to rotate and thereby raise or lower the grasping hooks 110.For example, the teeth of bevel gear 225 a mesh into the grooves ofbevel gear 235 a, and vice versa.

The arc range of motion of the grasping hooks 110 can be varieddepending on the particular angles (the “meshing angle”) that the bevelgears 225 have relative to the bevel gears 235 when the two gear setsmesh. The meshing angle is calculated by summing the respective pitchangles of the bevel gears. For example, the exemplary embodiment in FIG.2 has a meshing angle of 45 degrees created by the first pair of bevelgears 225 and the second pair of bevel gears 235 both having pitchangles of 22.5 degrees. Other gear meshing angles can be implemented byimplementing bevel gears having different pitch angles, such as 15, 30,60, 75, or 90 degrees, depending on the desired range of motion for theattachment mechanism 100. Further, in one or more embodiments, the bevelgears 235 have the same or similar size and throated configuration asthe bevel gears 225. Each of the bevel gears is not required to be anidentical size, as, for example, larger or smaller bevel gears 235 canbe implemented in order to compensate for a larger or smaller meshingangle.

Many subsea surfaces, such as pipelines, have ferromagnetic properties.To increase adherence to the inspection surface, in one or moreembodiments, magnetic material can be embedded in the grasping hooks 110at or adjacent to the first free end. The magnetic material can be madeof iron, nickel, cobalt, rare earth metals, and alloys thereof.

Subsea surfaces also can also be covered in protective coating, such asfor cathodically protected pipelines. In one or more embodiments, thegrasping hooks 110 are covered with a rubber coating for preventingsubsea structure damage when the hooks clamp onto the structure. In oneor more embodiments, protective padding or cushion is fixed to the frontsurface of the ROV 105 that is between the coupled first ends 115 of thegrasping hooks 110 such that if the ROV contacts the structure surface,no or little damage is done to the surface. In one or more embodiments,a rolling element is fixed to the underside of the grasping hooks and/orthe front surface of the ROV 105 between the coupled first ends 115. Forexample, the rolling element can include one or more rollers, ballbearings, or wheels such that when the ROV 105 is clamped to thesurface, if the ROV activates thrusters, the grasping hooks 110 and/orROV body rolls across the structure circumferentially. This provides anadditional degree of freedom (i.e., a pitch angle) that allows for moreeffective cleaning and inspection methods.

With reference now to FIG. 3, an attachment mechanism 300 for securing aROV to a subsea structure in accordance with at least one embodiment ofthe present application is provided. If the subsea structure to beinspected or cleaned is embedded in the earth or situated on the seabed,a negatively buoyant ROV 305 can be implemented. Negatively buoyant ROVsprimarily operate by crawling along the seabed using treads or wheels.While attachment mechanism 300 is advantageously implementable withnegatively buoyant ROVs, the attachment mechanism 300 according to oneor more embodiments herein can be used with other traditional ROVs(e.g., ROV 105). ROV 305 includes horizontal thrusters 310 and verticalthrusters 315 for navigating to and along the seabed. However, once onthe seabed, thruster utilization is preferably minimized by employingmotorized treads 320 as the primary means for moving along the seabed,as thruster utilization on the seabed can agitate the seabed by stirringup loose, soft sand, thereby limiting operator visibility of theenvironment.

Attachment mechanism 300 includes a rigid holder 325 having a first orattachment end 330 that is mounted at the front surface of the ROV 305.In one or more embodiments, the rigid holder 325 extends from its firstend to a second end 335 along a circular arc of up to 180 degrees (asillustrated). In other embodiments, the rigid holder 325 extends in astraight line without a bend. The leading surface of the second end 335can be shaped into a rounded or other aerodynamic head to facilitatepassing through the water with minimized friction. In one or moreembodiments, the second end 335 includes a mechanical stop 340. Forexample, the mechanical stop 340 can be a portion of the second end 335that extends downwardly from the longitudinal span of rigid holder 335to define a lip, the lip having an underside surface that is oppositelyfacing from the leading surface of the second end. The mechanical stop340 can also include other flanges, blocks, or impediments.

In one or more embodiments, the attachment mechanism 300 includes aspring loaded swing arm 345 coupled to the rigid holder 325 at a pivotpoint 350 about which the swing arm can rotate. The pivot point 350 isdisposed adjacent to the second end 335 at a point near the mechanicalstop 340 such that at rest, the swing arm 345 hangs substantiallyperpendicular to the seabed in a rest position. A spring means 355 isdisposed between the mechanical stop 340 and the swing arm 350. Thespring means 355 provides a spring force that urges the swing arm 345toward the mechanical stop 340. For example, if the mechanical stop 340defines a lip as shown in FIG. 3, the spring means 355 is fixed to theunderside of that lip and biased to maintain the swing arm 345 restposition orientation relative to the rigid holder 325. The spring means355 can be a compression spring, tension spring, or other known springmeans. In one or more embodiments, a freely rotatable rolling element360 is embedded in the swing arm 345. The rolling element 360 caninclude one or more rollers, ball bearings, wheels, and the like.

The operation of attachment mechanism 300 is illustrated by FIGS. 4A-4B.As shown in FIG. 4A, the thrusters 310, 315 and/or motorized tread 320actuate the ROV 305 to bring it into proximity with a subsea structure405 to be cleaned or inspected until the swing arm 345 contacts a firstportion of the structure. As the ROV 305 continues to advance toward thesubsea structure 405, such that the rolling element 360 of the swing arm345 moves across the subsea structure surface to a second portion ofthat surface, a reaction force is generated. The reaction force urgesthe swing arm 345 to pivot inward toward the rigid holder 325 of the ROV305 about the pivot point 350. As the swing arm 345 pivots, the springmeans 355 stretches and extends to provide a spring tension force thaturges the swing arm downward toward the outer surface of the subseastructure 405, causing the swing arm to continue to abut the outersurface as the ROV 305 moves forward. During pivoting, the rollingelement 360 facilitates the circumferential sliding of the swing arm 345along the outer surface of subsea structure 405. In this way, therolling element 360 provides an additional degree of freedom in thepitch angle plane.

When the ROV 305 moves forward enough such that the free end of theswing arm 345 passes by the apex of the subsea structure 405, the springtension force provided by the spring means 355 overcomes the reactionforce and frictional surface forces from the subsea structure to pivotthe swing arm back toward the mechanical stop 340 in the rest position,as illustrated by FIG. 4B. The mechanical stop 340 then prevents furtheroutward rotation. In this way, the swing arm 345 serves to embrace thesubsea structure 405 and hold the ROV 305 in place. In one or moreembodiments, the ROV 305 embraces the subsea structure 405 by the swingarm 345 contacting a third portion of the subsea structure 405, in whichthe third portion is approximately diametric to the first portion of thesubsea structure. Thereafter, the ROV 305 can perform cleaning andinspection tasks using, for example, cleaning nozzles, inspection arms,and other tools (not shown) while compensating for reaction forcescreated by performing such tasks. To further counteract reaction forces,an additional rolling element (that can be the same or similar torolling element 360) can be fixed to the front surface of the ROV 305below the rigid holder 325, such that when the swing arm 345 is in theclamped position as in FIG. 4B, the vertical thrusters 315 can beutilized to further facilitate the attachment mechanism 300 slidingacross the subsea structure. In one or more embodiments, protectivepadding or cushioning is fixed to the front surface of the ROV 305 belowthe rigid holder 325 such that if the ROV contacts the subsea structure405 surface, no or little damage is done to the surface or the ROV.

As will be appreciated, the swing arm 345 has a length that is selectedin view of the overall distance that the rigid holder 325 displaces thepivot 350 from the attachment point 330 to the rover 305, and in furtherview of the anticipated diameter (or other dimension) of the object tobe grasped, such as the subsea structure 405. As illustrated in FIGS. 4Aand 4B, the swing arm pivots in response to forces imparted by thesubsea structure 405 to an upward position and returns to its restposition (FIG. 4B) after the rover 305 has advanced leftward in thefigures until the subsea structure 405 is proximate the forward end ofthe rover. Thereafter, the rover can move in reverse to bring the swingarm 345 into sure contact with the subsea structure (namely, the leftside of the subsea structure, as illustrated).

With reference now to FIGS. 5A-C, an attachment mechanism 500 forsecuring a ROV to a subsea structure in accordance with at least oneembodiment of the present application is provided. The attachmentmechanism 500 is coupled to a ROV 505 in the same or similar way asattachment mechanism embodiments are coupled ROV 105 or ROV 305 above,and, as described below, is driven by a mechanism within the ROV toprovide its attachment functionality. The attachment mechanism 500 isconfigured to provide a finger-like clamping mechanism that enables theROV 505 to clamp to a variety of subsea structures (e.g., subseastructure 510, illustrated as a pipeline in FIG. 5B) having variousgeometries and diameters, and without implementing thrusters as a partof the attachment mechanism. During operation, the attachment mechanism500 has an extended or unclamped state, as shown by FIG. 5A, in which aplurality of linked segments 515 are horizontally coaxially aligned inseries. As the ROV 505 approaches a subsea structure 510, preferablyfrom above the structure, as shown by FIG. 5B, the plurality of linkedsegments 515 are actuated to curl about the outer surface of the subseastructure and clamp the ROV in place during cleaning or inspection (a“clamped state”). To facilitate clamping, in one or more embodiments,the plurality of linked segments 515 can be coated in rubber material toincrease the grip friction and reduce scraping at a subsea structuresurface. In one or more embodiments, magnets or electromagnets can bedisposed within and adjacent to the lower surface of the linked segments515 help stabilize the attachment mechanism 500 to the subsea structuresurface.

More particularly, the plurality of linked segments 515 are coupled at aplurality of pin joints 520, with a pin joint between each two linkedsegments. The linked segments 515 are machined so that each defines amechanical stop 525 at the upper surface of a given segment. Forexample, as shown in FIG. 5C, the plurality of linked segments 515 a,515 b can be machined to define a pair of corresponding notches 517, 518that enable each segment to be seated in the segment that follows it,thereby functioning as a mechanical stop 525. In one embodiment, a firstrectangular notch 517 a is disposed at the upper left portion of thelinking segment 515 a and a second rectangular notch 518 a is disposedat the lower right portion of linking segment 515 a. In this way, thelinking segment 515 a is S-shaped, though the upper and lower surfacescan be rounded or concave to adapt to the outer surface of a subseastructure 510. As can be seen, the upper right portion of linkingsegment 515 a can be seated in the first notch 517 b of the linkingsegment 515 b, which is the next linking segment, whereas the lower leftportion of the linking segment 515 b is seated in second notch 518 a ofthe linking segment 515 a. The two linking segments 515 a, 515 b arethen coupled at a pin joint 520 b. This arrangement provides amechanical stop 525 that allows linking segment 515 a to rotate downwardto a certain angle (e.g.,5, 10, or 15 degrees), but the first notch 517prevents upward rotation of the plurality of linking segments beyondapproximately the zero degree level horizontal plane (i.e.,substantially straight). This linking arrangement continues for each ofthe plurality of linking segments 515, except for the first linkingsegment (which in some arrangements, does not include a first notch 517,as nothing links to the front of it), and the last linking segment(which in some arrangements, does not include a second notch 518, asthat portion of the linking segment can be coupled to the ROV 505).Further, each linking segment 515 in one or more embodiments ispreferably identical to all the others (except the first and lastsegment as above), although they could differ in construction. In thisway, linking segments 515 can be added or removed to increase ordecrease the length of the attachment mechanism 500 needed to clean orinspect the subsea structure 510.

As buoyancy, current, and gravitational effects are inherent in a subseaenvironment, the attachment mechanism 500 needs to be actuated tooperate from the unclamped to the clamped state by an actuationmechanism. In one or more embodiments, to control the clampingoperation, the actuation mechanism includes an extension wire 530connected to an extension pulley 535, and a retraction wire 540connected to a retraction pulley 545. The extension wire 530 and theretraction wire 540 are flexible wires or cables that are supportedwithin the plurality of linking segments 515 and terminate at one endwithin the first linking component, and terminate at the pulleys thatare housed within the ROV 505 at the other end. In one or moreembodiments, the extension wire 530 is supported above the plurality ofpin joints 520, and the retraction wire 540 is supported below the pinjoints.

The extension pulley 535 and the retraction pulley 545 are housed withinthe ROV 505 and can be motorized or spring loaded pulleys for actuation,and are configured for synchronized rotation, though in oppositedirections (i.e., if the extension pulley rotates clockwise, theretraction pulley rotates counter-clockwise). Both the extension wire530 and the retraction wire 540 are made of materials capable of bendingupwards and downwards. Thus, during actuation of the extension pulley535 and retraction pulley 545 via a motor or by releasing or compressinga spring force, the wires extend or retract correspondingly into the ROV505 around the respective connected pulley, thereby rotating theplurality of linked segments 515 inward or outward.

In one or more embodiments, the attachment mechanism 500 includes one ormore locking mechanisms 550 in connection with the extension wire 530and/or the retraction wire 540 for limiting pulley motor powerconsumption during clamping operation. The locking mechanism 550 limitspower consumption by locking the extension wire 530 and retraction wire540 in place during surface cleaning or inspection, without requiring amotor to continually drive the extension pulley 535 and retractionpulley 545 to maintain contact between the plurality of linking segments515 and the surface, as reaction forces are generated by cleaning orinspection. The locking mechanisms 550 are typically housed within theROV 505 adjacent to the extension pulley 535 and retraction pulley 545,though the locking mechanism could be arranged within the plurality oflinking segments 515 so long as it can serve to communicate with thepulley motor(s). In some arrangements, a single locking mechanism 550 ishoused within the ROV 505 between the extension wire 530 and retractionwire 540. In other arrangements, a first locking mechanism is housed inthe ROV 505 below and in connection with the extension wire 530, and asecond locking mechanism is housed in the ROV above and in connectionwith the retraction wire 540.

While the exemplary embodiment shown in FIGS. 5A-C contemplates rotatingthe attachment mechanism downward to adhere to a subsea surface, in oneor more embodiments, the actuation mechanism can include additionalmotors, wires, and pulleys arranged in a similar way as provided aboveto introduce addition clamping angles. For example, an additionalmotor/wire/pulley system can be arranged to provide sideways or a slightupward movement to the plurality of linked segments 515. Such upwardmovement can comprise angles 0-15 degrees from the horizontal plane ofthe linked segments 515 at a level orientation. In this way, theattachment mechanism 500 can be adapted to clamp to vertically orientedstructures and other structure orientations.

Notably, the figures and examples above are not meant to limit the scopeof the present application to a single implementation, as otherimplementations are possible by way of interchange of some or all of thedescribed or illustrated elements. Moreover, where certain elements ofthe present application can be partially or fully implemented usingknown components, only those portions of such known components that arenecessary for an understanding of the present application are described,and detailed descriptions of other portions of such known components areomitted so as not to obscure the application. In the presentspecification, an implementation showing a singular component should notnecessarily be limited to other implementations including a plurality ofthe same component, and vice-versa, unless explicitly stated otherwiseherein. Moreover, applicants do not intend for any term in thespecification or claims to be ascribed an uncommon or special meaningunless explicitly set forth as such. Further, the present applicationencompasses present and future known equivalents to the known componentsreferred to herein by way of illustration.

The foregoing description of the specific implementations will so fullyreveal the general nature of the application that others can, byapplying knowledge within the skill of the relevant art(s) (includingthe contents of the documents cited and incorporated by referenceherein), readily modify and/or adapt for various applications suchspecific implementations, without undue experimentation, withoutdeparting from the general concept of the present application. Suchadaptations and modifications are therefore intended to be within themeaning and range of equivalents of the disclosed implementations, basedon the teaching and guidance presented herein. It is to be understoodthat the phraseology or terminology herein is for the purpose ofdescription and not of limitation, such that the terminology orphraseology of the present specification is to be interpreted by theskilled artisan in light of the teachings and guidance presented herein,in combination with the knowledge of one skilled in the relevant art(s).

While various implementations of the present application have beendescribed above, it should be understood that they have been presentedby way of example, and not limitation. It would be apparent to oneskilled in the relevant art(s) that various changes in form and detailcould be made therein without departing from the spirit and scope of theapplication. Thus, the present application should not be limited by anyof the above-described example implementations.

What is claimed:
 1. An attachment mechanism suitable for securing aremotely operated vehicle (ROV) to a subsea structure, comprising: arigid holder having at first end mounted to the ROV and a second endthat is free, the rigid holder having a mechanical stop disposed at thesecond end and a pivot point adjacent to the second end; a swing armcoupled to the rigid holder at the pivot point, the swing arm having arolling element embedded therein and in a rest orientation; and a springmeans disposed between the mechanical stop and the swing arm, therebyproviding a tension force to the swing arm, wherein the swing arm isconfigured to rotate inward toward the ROV and away from the restorientation until the tension force overcomes a reaction force generatedfrom contact with the subsea structure to return the swing arm to therest orientation.
 2. The attachment mechanism of claim 1, wherein therigid holder extends from its first end to the second end along acircular arc of 0 to 180 degrees.
 3. The attachment mechanism of claim1, wherein the mechanical stop includes a lip, the lip having anunderside surface that is opposite to a leading surface of the secondend that the swing arm cannot rotate beyond.
 4. The attachment mechanismaccording to claim 1, wherein the rigid holder extends from its firstend to the second end without a bend.
 5. The attachment mechanismaccording to claim 1, wherein the second end of the rigid holder isrounded.
 6. The attachment mechanism according to claim 1, wherein themechanical stop includes one or more flanges.
 7. The attachmentmechanism according to claim 1, wherein the rest orientation orients theswing arm substantially perpendicular to a seabed.
 8. The attachmentmechanism according to claim 1, wherein the spring means is acompression spring.
 9. The attachment mechanism according to claim 1,wherein the spring means is a tension spring.
 10. The attachmentmechanism according to claim 1, wherein the rolling element includes oneor more rollers, one or more ball bearings, or one or more wheels.
 11. Amethod of attaching a remotely operated vehicle to a surface of a subseastructure, the remotely operated vehicle initially in a restorientation, the remotely operated vehicle being of the type having arigid holder coupled to a swing arm with a rolling element embeddedtherein and a spring means disposed between the rigid holder and theswing arm, the method comprising: contacting a first portion of thesubsea structure with a first face of the rolling element; advancing theremotely operated vehicle in the direction of the subsea structure suchthat the first face of the rolling element contacts a second portion ofthe subsea structure and generates a reaction force that causes theswing arm to pivot toward the rigid holder and increase a tension forcein the spring means; advancing the remotely operated vehicle in thedirection of the subsea structure such that the first face of therolling element passes an apex of the subsea structure and the tensionforce stored in the spring means is greater than the reaction forceexerted on the swing arm; and pivoting the swing arm away from the rigidholder back toward the rest orientation by releasing the tension forcein the spring means.
 12. The method according to claim 11, whereinpivoting the swing arm away from the rigid holder back toward the restorientation causes the swing arm to contact a third portion of thesubsea structure that is approximately diametric to the first portion ofthe subsea structure.
 13. The method according to claim 11, wherein thesteps of advancing the remotely operated vehicle further compriseactivating one or more horizontal thrusters.
 14. The method according toclaim 11, wherein the steps of advancing the remotely operated vehiclefurther comprise activating one or more vertical thrusters.
 15. Themethod according to claim 11, wherein the steps of advancing theremotely operated vehicle further comprise activating one or moremotorized treads.